When such liquefied products are ignited, all give up water with a release of heat which intensifies the gaseous release of the product and provokes an increase of flame. Previously, the foams employed for extinction of fires were thus hardly effective.
There has been used to remedy this disadvantage a product and a system for obtaining a maximum amount of foam from a minimum amount of water, an expansion of one hundred to three hundred times the initial volume being obtained, a greater expansion producing a foam which is too light and can be carried away by the convection currents produced by the fire. Unfortunately, in practice to obtain such expansion, it is necessary to employ the major portion of the available energy (discharge pressure) whereby there is no longer sufficient energy to obtain the necessary range for manual use. Because of this fact, the utilization of a mobile material remains impossible for large discharges.
There has also been tried the utilization of foam called "low expanded foam" that is to say representing six to ten times the initial volume. In this case, the transformation of energy is relatively low which permits obtaining an appreciable range for an ordinary incendiary fire. However, with respect to a liquid gas fire, at low temperature, this solution produces a release of water, therefore of heat, so significant taking into account what is tolerable, that extinction of the fire is rendered impossible because of the transformation of the liquid to gas. The application of the above two foam products, therefore, remains very limited, the first lacking the range, the second giving up too much heat by the presence of water in great quantity.